Improvements in supporting slabs during continuous casting

ABSTRACT

A slab shaped strand of metal is continuously cast by pouring metal into the top of a tubular mold and withdrawing a partially solidified strand from beneath the mold. Grid strips extend down from the bottom of the mold and press against the flat sides of the strand to maintain concavities therein during the initial cooling period. The grid strips then terminate; and edge rolls then press inwardly against the narrow edges of the slab to maintain the sidewall concavities.

United States Patent 1191 1111' 3,765,472 I Rossi 1 Oct. 16, 1973 [54] IMPROVEMENTS IN SUPPORTING SLABS 3,416,222 12/1968 Pearson 164/82 X U G CONTINUOUS CASTING 3,515,202 6/1970 Bick et al 164/89 [76] Inventor: Irving Rossi, Dunros Farm, James O G ATENTS OR APPLiCATIONS t, M ist 07960 702,719 1/1954 Great Britain 164/283 [22] Filed: Feb. 11, 1971 Primary ExaminerR. Spencer Annear [211 App! 114592 Attorney-Nichol M Sandoe et a1.

Related US. Application Data [63] Continuation-impart of Ser. No. 111,488, Feb. 1, [57] ABSTRACT A slab shaped strand of metal is continuously cast by [52] us. c1 164/282, 164/283 s Pwring metal the top tubular and with [51 1111.01 B22d 11/12 drawing Partially mlidified Strand beneath the [58] Field of Search 164/82, 89, 273 R, Grid Smp5 extend fmm the 164/282 283 mold and press against the flat sides of the strand to maintain concavities therein during the initial cooling [56] References Cited I period. The grid strips then terminate; and edge rolls UNITED STATES PATENTS then press mv ardly against the narrow edges of the slab to mamtam the sidewall concavmes.

2,698,467 l/l955 Tarquinee etal l64/283X 3,375,864 4/1968 Butkevich et a1 164/282 I 6Claims,7Drawing Figures e. a 1 I 7L -30 Z K) Z T i; a. T

1 Twit 1H t I 3 I r E: E l 3 f 1 6. 1 631, 1 1o T 1 I 50 49 4e 3o r 21-- 32 IMPROVEMENTS IN SUPPORTING SLABS DURING CONTINUOUS CASTING This application is a continuation-in-part of my copending application Ser. No. l I 1,488 filed Feb. 1, I971.

. The invention pertains to continuous metal casting and provides improvements applicable to the methods and apparatus therefor disclosed in my above men'- tioned parent application.

According to the invention of said earlier application, metal is cast from a molten state in a tubular mold having a pair of oppositely disposed sidewalls which are inwardly arched toward one another for casting. the metal into a relatively wide faced slab consisting of an outer shell of solidified metal and a molten core, the slab faces of which are concavely arched transversely thereof to prevent bulging due to the ferrostatic pressure exerted by the molten core. The case slab is received from the mold exit between edge rolls which bear against the opposite edges of the slab with sufficient force to buttress the slab edges and the concave side faces thereof against such bulging.

A problem arises, however, in that it is difficult to control exactly the temperature of a molten metal, such as steel, when it arrives at the casting machine, usually by ladle from a basic oxygen furnace or the like. To compensate for the time interval delay involved the steel ordinarily leaves the furnace with some degree of superheat which must be lost before the metal can be brought down to temperature of about 2600-2800F. at which the solidification process can begin, as otherwise there is a tendency for rupture of the extemely thin-walled shell of the slab an initially cast. This tendency is aggravated by the fact that the mold below the metal-mold break away area is a poor cooling region by cordance with a further embodiment of the invention;

while FIG. 7 is a transverse sectional view of FIG. 6 as taken at 77 thereof.

Referring to FIGS. l-3 inc., a vertically disposed tubular copper mold 10, is jacketed as at 11, for circulation of a liquid coolant, such as cold water, about the mold as at 12, the coolant being supplied thru inlet and outlet pipes 13 and 14. As shown in FIG. 2, the mold as viewed in transverse section is formed with a pair of oppositely disposed and relatively wide sidewalls which are inwardly arched toward one another, as at 15, 16, and with a pair of oppositely disposed and relatively narrow end walls which are substantially parallel to one another, as at 17, 18. The end walls are bevelled at the corners, as at 19, 20, and are joined to contiguous portions of the sidewalls which are substantially parallel to one another, as at 21, 22, and which in turn are joined to the inwardly arched sidewall portions 15, 16, in the manner shown in the drawing. As is also shown in FIG.

- 2, the coolant jacket 11 is of the same configuration as reason of the spacing thus produced between the metal v and the mold due to shrinkage of the metal in passing from the molten to the solid state. It, therefore, becomes necessary to spray the casting intensely with a liquid coolant when it leaves the support area of the mold.

In accordance with the present invention this difiiculty is overcome by mechanically bracing the cast slab on its wide concave faces while intensely spraying the.

same as the casting exits from the mold.

This dual action is accomplished in accordance with FIGS. 2 and 3 being transverse sections at 2--2 and g 33 of FIG. I. FIG. 4 is a view in front elevation of an assembly similar to FIG. 1, but showing a modified form of slab face buttressing grid structure,

FIG. 5 being a transverse section at 5-5 of FIG. 4. FIG. 6 is a view in elevation, similar to FIG. 4, but showing a slab face buttressing plate structure, in acthe mold 10, but of greater transverse dimensions and is disposed coaxial with the mold as shown in order to provide a substantially constant spacing between the walls of the jacket and mold.

Referring to FIG. I there is mounted above the mold, a tundish 25, having a central opening 26, for teeming molten metal, such as steel, from a tundish charge thereof as at 27, thence thru the opening 26 and as at 28, into the mold cavity, as at 29. Owing to the coolant action of the coolant jacket 11, 12, the liquid metal in contact with the mold, quickly solidifies, as at 30, to cast the molten metal into a continuous slab, as at 31, consisting of an outer solidified shell 30 and a molten metal core 32. The metal in passing from the molten state shrinks away from the mold over a break away area as at 30a, leaving a space between the mold and the slab shell, as at 30b. As shown in FIGS. 2 and 3, the solidified slab shell 30, as cast by the mold has the same configuration in transverse section as the mold cavity, with the wide faces of the slab shell concavely arched, as at 34, 35, andterminating in flattened portions, as at 36, 37, joined by bevelled edges, as at 38, 39, to the substantially parallel end walls 40, 41 of the slab shell.

In accordance with the FIGS. 1 and 3 embodiment of the present invention, there are mounted beneath the horizontally disposed and spaced cross bars, as at 49.

As shown in FIG. 3 the grids 45 and 46 are of arcuate configuration corresponding to the transverse arcuate configurations of the concave slab faces 34 and 35, and the grids are so mounted as shown that they press against and buttress the concave slab faces against rupture or tendency to bulge.

As the slab strip is fed between the grids it is subjected to intense cooling action by cold 'water sprays from spray nozzles, as at 50, 51, the major portion of which is sprayed onto theconcave surfaces of the slab strip thru the grid openings, but a portion of which is also sprayed onto the grids themselves to prevent overheating the same. The grids are preferably made of cooper or other heat resistant metal of high thermal conductivity.

Reverting to FIG. I, the slab strip as it exits from the bracing grids 45, 46, is received between a pair of edge withdrawal away from the mold, as at 30a. Another purpose is that by compressing the strip widthwise, it also increases the concavity of the concave slab surfaces as a further assurance against bulging or rupture of the thin walled slab strip as initially formed.

, FIGS. 4 and 5 show a modified type of grid structure for buttressing the concave slab surfaces against rupture of the slab shell 30. In this embodiment-the vertical members of the grid structure comprise heavy copper plates, as at 60, 61, which are maintained in spaced apart parallel relation as shown by means of spaced apart, horizontal cross bars, as at 63, 64, 65, integrated as by welding to the vertical members. As shown in FIG. 5, the grids are of arcuate configuration in transverse section and the vertical members bear against the arcuate surfaces 34 and 35 respectively of the slab shell 30 to buttress the same against rupture. The vertical members are provided with a series of holes extending therethrough, as at 67, 68, and referring to FIG. 5, a series of spray nozzles is mounted on each side of the slab strip 31, as at 70, 71, for spraying a coolant liquid such as cold water, as at 72, 73, onto the concave slab surfaces through the grid openings between the vertical and horizontal members and also through the holes, as at 67, 68, through the vertical members.

In the embodiment of FIG. 6, the buttressing members comprise triangular plates as at 80, of arcuate transverse section as shown in FIG. 7, in conformity with the contiguous concave faces, as at 35, of the slab shell 30. Also as shown in FIG. 7, these plates bear against the concave surfaces of the slab for buttressing the same against rupture. The plates are provided with a series of perforations extending therethrough, as at 81, and a series of spray nozzles are mounted opposite each plate, as at 82, for spraying cold water or other coolant liquid, through the plate perforations 81 onto 7 the faces of the slab strip.

I claim 1. Metal casting apparatus comprising a tubular mold having means for cooling the same, said, mold having a pair of oppositely disposed wide sidewalls inwardly arched toward one another and interconnected at their edges by oppositely disposed narrow edge walls, said mold being mounted with one end above the other, the casting molten metal into a continuous slab comprising an outer shell of solidified metal enclosing a molten core thereof and having inwardly arched wide sidewalls interconnected by narrow edge walls, bracing means adjacent the exit from said mold adapted to bear against the concavely arched wide sidewall surfaces of the cast slab shell for mechanically bracing the same i against rupture, means for cooling said slab while so braced and support means below said bracing means for engaging only the opposite edge walls of said slab and for applying compressive forces to the slab widthwise thereby to retain the inwardly arched configuration of said sidewalls.

2. Apparatus according to claim 1 wherein said bracing means includes a pair of reticulated and substantially rigid bracing members mounted in spaced apart relation substantially parallel to the axis of said mold, said bracing members being inwardly arched toward one another and mounted respectively adjacent the inwardly arched sidewalls of said mold, and means disposed adjacent said bracing members for spraying a coolant liquid against the arched faces of said slab thru reticulations of said bracing members.

3. Apparatus according to claim 2 wherein each of said bracing members comprises a metal grid composed of spaced bars extending parallelvto the axis of said'mold and spaced cross bars integrated thereto, said cross bars being shaped to impart an arcuate contour of said grid.

4. Apparatus according to claim 3 wherein said spaced parallel bars are of substantial width and are perforated at spaced intervals for spraying said coolant fluid therethrough into said slab.

5. Apparatus according to claim 2 wherein each of said bracing members comprises a substantially triangular metal plate mounted with one edge substantially parallel to and adjacent the exit of said mold, said plates being perforated for spraying said coolant therethrough into said slab.

6. The method of continuous metal casting which comprises: casting said metal from a molten state into a continuous slab comprising a thin walled shell of solidified metal and a core of molten metal, said shell having formed across its width, oppositely disposed concavely arched surfaces, subjecting said arched surfaces as cast to mechanical bracing across their width to prevent rupture thereof and thereafter removing said mechanical bracing and subjecting the edges of said slab to mechanical bracing to apply compressive force to the slab widthwise to retain the concavely arched configuration of said sidewalls. 

1. Metal casting apparatus comprising a tubular mold having means for cooling the same, said mold having a pair of oppositely disposed wide sidewalls inwardly arched toward one another and interconnected at their edges by oppositely disposed narrow edge walls, said mold being mounted with one end above the other, the casting molten metal into a continuous slab comprising an outer shell of solidified metal enclosing a molten core thereof and having inwardly arched wide sidewalls interconnected by narrow edge walls, bracing means adjacent the exit from said mold adapted to bear against the concavely arched wide sidewall surfaces of the cast slab shell for mechanically bracing the same against rupture, means for cooling said slab while so braced and support means below said bracing means for engaging only the opposite edge walls of said slab and for applying compressive forces to the slab widthwise thereby to retain the inwardly arched configuration of said sidewalls.
 2. Apparatus according to claim 1 wherein said bracing means includes a pair of reticulated and substantially rigid bracing members mounted in spaced apart relation substantially parallel to the axis of said mold, said bracing members being inwardly arched toward one another and mounted respectively adjacent the inwardly arched sidewalls of said mold, and means disposed adjacent said bracing members for spraying a coolant liquid against the arched faces of said slab thru reticulations of said bracing members.
 3. Apparatus according to claim 2 wherein each of said bracing members comprises a metal grid composed of spaced bars extending parallel to the axis of said mold and spaced cross bars integrated thereto, said cross bars being shaped to impArt an arcuate contour of said grid.
 4. Apparatus according to claim 3 wherein said spaced parallel bars are of substantial width and are perforated at spaced intervals for spraying said coolant fluid therethrough into said slab.
 5. Apparatus according to claim 2 wherein each of said bracing members comprises a substantially triangular metal plate mounted with one edge substantially parallel to and adjacent the exit of said mold, said plates being perforated for spraying said coolant therethrough into said slab.
 6. The method of continuous metal casting which comprises: casting said metal from a molten state into a continuous slab comprising a thin walled shell of solidified metal and a core of molten metal, said shell having formed across its width, oppositely disposed concavely arched surfaces, subjecting said arched surfaces as cast to mechanical bracing across their width to prevent rupture thereof and thereafter removing said mechanical bracing and subjecting the edges of said slab to mechanical bracing to apply compressive force to the slab widthwise to retain the concavely arched configuration of said sidewalls. 